Vanderhoof Uses Landsat to Look at the Ecological Impacts of Fire and Water

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Melanie Vanderhoof works in the realms of fire and water, studying how they change landscapes and influence the ecological rhythms of Nature.

As a research geographer with the U.S. Geological Survey’s (USGS) Geoscience and Environmental Change Science Center in Denver, CO, Vanderhoof focuses on everything from the post-fire regeneration of forests to how wetlands and waterways are impacted by floods and droughts.

She relies on Landsat’s rich and dense archive, as well as other remote-sensing platforms, to do that.

Vanderhoof’s work helps communities evaluate risk at the intersection of wildlands and urban areas, where fire can wreak immense havoc. Her research on the multi-decadal patterns of river and lake flooding can help in the design of more flood-resistant communities. And her use of cloud-based data platforms to quickly analyze change over time is providing decision-makers with the information they need at much less cost than it used to take to do such analysis.

She talked about all that in this recent conversation.

How did you get into ecosystem change work?

“I’ve always been really interested in how ecosystems work. I spent a lot of time wandering through the forests of New Hampshire as a kid. Most ecosystems are such dynamic and resilient environments, and I think one of the best ways to see that in action is by studying how they respond to a large disturbance event, or a substantial change, like an insect outbreak, a fire, or an extreme climate event.”

Why is that work important?

Color photo of Melanie Vanderhoof

Melanie Vanderhoof, pictured with the graphic for the USGS EROS podcast "Eyes on Earth."

Well, in addition to having profound impacts on how these ecosystems function, these disturbances can be massively expensive for local communities. For example, wildfires can threaten and burn houses in the wildland-urban interface. Floods can damage housing, and delay or damage crops. Understanding the disturbance history or the natural range of variability can help communities evaluate risk and protect themselves against future threats.”

When you research post-fire regeneration across the western U.S., what specifically are you looking at and why?

“Over the last five to 10 years, there have been a number of field-based studies in the U.S., most often across the southern Rockies, in New Mexico, Arizona, and Colorado, that have found limited or no regeneration of some conifer species following fire events. There’s increasing concern that as climate patterns change, more forests may transition to grassland or a shrub systems, which could have pretty dramatic impacts for wildlife, carbon storage, and climate-vegetation feedbacks. We are interested if this concern is just limited to the southern range of some of these conifer species, or if the pattern persists at the scale of the western United States. So, to look across that big of an area, we’re relying on the Landsat archive.”

You co-authored the Landsat Burned Area Product. What is this product, and what is the value of using Landsat to produce it?

“The Landsat Burned Area Product uses the entire Landsat archive, so 1984 to present, across the conterminous United States, to map and track burned area extent every eight to 16 days, at 30-meter resolution. And because the product generation is largely automated, we now have a better understanding about how fire extent may have changed over the last 35-plus years.”

Haven’t others been looking at look at burned area extent through time?

“Prior to our product, there were and continue to be a number of other U.S. and global fire products, and each one has its own contribution and value. But one of the challenges that U.S. fire products have faced is that they often rely on fires being reported, and reporting efforts can be quite uneven over time. That means it can be harder to understand at a national scale how fires are changing. Because we have 30-meter resolution with Landsat, we can map heterogeneity within a given fire, so we can distinguish relatively small unburned patches within a fire that might serve as a seed source and wildlife refuge as the ecosystem recovers.”

Does the burned area product help you understand why areas may have burned?

“We’ve been scheming with scientists from the University of Colorado in Boulder about how we might in the future be able to tie different fire datasets together to provide a more complete understanding of not just where, but also why fires are occurring, and how burn severity and fire spread might be changing over time.”

How would that information be valuable to forest managers?

“It helps you understand what the current condition is of the forest, and that enables you to have more information, and more data, to be able to make decisions on how to manage and move forward. It also helps you to better predict the risk of that area burning again, particularly when you’re looking at areas that are close to communities.”

Those predictions could lead to such things as doing prescribed burns to remove fuel loads?

“Exactly. At a state level, a local level ... actively doing prescribed burns and doing understory clearing can be really expensive. With limited resources, we need to be able to figure out how to prioritize and most efficiently use that funding to make our forests healthier.”

Some of your recent research has focused on the condition of riparian corridors. Why?

“Riparian corridors are incredibly important ecologically. They store water, nutrients, and sediments. They reduce downstream flood impacts and hold non-point source pollution. They provide corridors for animals to move and migrate, particularly through environments that can be hostile to wildlife, such as arid, urban, or agricultural areas. And they sustain fish habitat by lowering stream temperatures and contributing woody debris. Globally, the degradation of riparian areas is a major issue. As rivers become more regulated through ... diversions and pumping, these activities tend to alter the timing and the magnitude of flow, and often end up degrading the riparian corridors.”

Why is the movement of surface water important?

“Information on our surface water is really fundamental to the economy, to protecting life and property, and to help us effectively manage the nation’s water resources. But, the amount of surface water and how it’s distributed is in constant flux and reacts to episodic events like rainfall or drought, seasonal patterns in rainfall and snowmelt, as well as annual variability in precipitation timing and amount. Remote sensing plays a really important role in that it can help us understand the variability in surface water extent over time, as well as help us understand how sensitive watersheds are to that variability in climate.”

Why are you interested in temporary wetland loss versus permanent loss?

“Wetlands have a lot of similar functions to riparian areas in that they help abate floods, control erosion, sequester carbon, support biodiversity, improve water quality. So, a lot of important ecosystem services. But over the last 300 years or so, we’ve lost almost 90 percent of wetlands globally, and about 30 percent of wetland areas since 1970.”

What’s caused that loss?

“Wetlands can be degraded or lost through a variety of changes, but one of the major causes is changes in land use. For example, expansion of agriculture or urban development. These changes make it essential for us to not only monitor wetland extent and condition over time, but to also enhance our understanding of the causes and the spatial distribution of wetland loss and gain.”

Landsat helps with that monitoring?

“We’re now getting to the point where we can remotely track surface water extent over time. I see the next step as being able to separate temporary loss in surface water extent ... which might be attributable to, let’s say a drought year, but which can be expected to return when conditions become wetter ... from a permanent loss, for instance, when a development occurs. In one of our ongoing research projects, we’re using the Landsat archive to concurrently track surface water extent and land disturbance with the idea that most permanent wetland loss caused by land use change is likely to be associated with a disturbance event that we can also detect remotely.”

Who would use that information, and how?

“Many wetlands are regulated under the Clean Water Act, so this type of information is relevant for policy, but another potential application is in restoration. If we understand where the wetlands loss is happening, and the types of wetlands that the loss is happening to, then that information can help us prioritize where to restore wetlands in order to help maintain their ecosystem functions and services.”

 

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